不同图像尺寸的台式机和手机

Question

I just did a speed test on desktop & mobile on gtmetrix and have the error code: Serve Scaled Images - But only on the mobile speed test. The error reads as follows:

* * .jpg is resized in HTML or CSS from 1200x431 to 318x114. Serving a scaled image could save 520.9KiB (92% reduction).

Is there a specific code I can put with the image to have it one size when on mobile and leave the desktop one at the original/other size. Or is there another way such as serve a particular image for mobile (same image smaller size) then another image for serving desktops?

Thanks.

Answer 1

You can do like this and define different background url on different media queries for same class.

    /* Smartphones (portrait and landscape) ----------- */
@media only screen
and (min-device-width : 320px)
and (max-device-width : 480px) {
/* Styles */
}

/* Smartphones (landscape) ----------- */
@media only screen
and (min-width : 321px) {
/* Styles */
}

/* Smartphones (portrait) ----------- */
@media only screen
and (max-width : 320px) {
/* Styles */
}

/* iPads (portrait and landscape) ----------- */
@media only screen
and (min-device-width : 768px)
and (max-device-width : 1024px) {
/* Styles */
}

/* iPads (landscape) ----------- */
@media only screen
and (min-device-width : 768px)
and (max-device-width : 1024px)
and (orientation : landscape) {
/* Styles */
}

Answer 2

I think you might want something like this:

    var isMobile = {
    Android: function() {
        return navigator.userAgent.match(/Android/i);
    },
    BlackBerry: function() {
        return navigator.userAgent.match(/BlackBerry/i);
    },
    iOS: function() {
        return navigator.userAgent.match(/iPhone|iPad|iPod/i);
    },
    Opera: function() {
        return navigator.userAgent.match(/Opera Mini/i);
    },
    Windows: function() {
        return navigator.userAgent.match(/IEMobile/i);
    },
    any: function() {
        return (isMobile.Android() || isMobile.BlackBerry() || isMobile.iOS() || isMobile.Opera() || isMobile.Windows());
    }
};

if(isMobile.any()){
    // Mobile!
} else {
    // Not mobile
}

You can then do something like: (untested below(needs tweaking))

if(isMobile.any()){
img { height:140%;width:140%

You can alter the size of images through the style tag. img { should alter all <img src tags on the page as I've done it before. And a revision of the above code should alter it only for mobile or desktop computers.